Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 242344

Area Forecast Discussion
National Weather Service Burlington VT
744 PM EDT Sat Aug 24 2019

Clouds cover will finally begin to diminish late this afternoon into
this evening with mostly clear skies residing through the overnight
hours. Some patchy dense fog is possible tonight but will likely be
limited to favorable locations within the Green and Adirondack
Mountains. Sunday, Monday and Tuesday look to be very pleasant days
across the region with partly to mostly sunny skies and temperatures
in the 70s. The next chance of rain comes on Wednesday with a
weakening front moving toward the region. High pressure then looks
to redevelop across the region leading to another dry period of
weather for the second half of the upcoming week.


As of 742 PM EDT Saturday...No changes were needed with this
update. Clouds have pretty much dissipated across the region.
The exception is portions of southeastern VT where flow has
turned more easterly, allowing moisture to lift back into the
Greens. Some patchy fog will be possible late tonight in those
areas that remain clear and temperatures will drop down into the
mid 40s to mid 50s. The forecast has this all covered, so no
changes were needed.

Previous discussion...Clouds continue to be stubborn this
afternoon but it finally looks like there is an end in sight for
the abundant cloud cover. A strong subsidence inversion has
trapped moisture in the boundary layer so far today with the
vertical extent of these clouds just 1000 feet or so based off
webcam and model soundings. A shortwave approaching from the
northeast has already begun to break clouds out across the
Northeast Kingdom as subsidence behind the wave has helped to
scour our the cloud cover. Once the wave pushes through, we
should see increasingly clearing skies heading into the evening
and overnight hours which will allow temperatures to quickly
fall especially given how we underperformed on high temperatures
today due to the cloud cover. With temperatures falling quickly
tonight, patchy dense fog is expected once again across the
favorable locations in the Green and Adirondack Mountains. Any
fog that develops tonight will quickly mix out Sunday morning
with better heating as cloud cover should be much less abundant.

High pressure will continue to remain dominant on Sunday with partly
to mostly clear skies allowing temperatures to warm back into the
70s across the region. Chances for rainfall are nearly zero percent
but there is a small chance for a little drizzle across southern
Vermont during the late afternoon hours.


As of 306 PM EDT Saturday...Surface high pressure will continue to
hold over the region with an upper low across the Canadian maritimes
maintaining easterly flow over the region. This will advect a drier
air mass into the region. Another pleasant day is in store with
highs in the 70s. Winds begin to shift and come out of the south
overnight, so we begin a gradual warm up. Lows should be in the
upper 40s to mid 50s.


As of 306 PM EDT Saturday...For Tuesday, surface high pressure will
slide offshore and upper ridge will crest over the region. Deep
layer southwesterly flow will initiate a gradual warm-up trend.
Tuesday should be just a few degrees warmer with valleys approaching
the low 80s. A north-south oriented front begins to move into the
region in the overnight hours Tuesday into Wednesday. Vorticity will
begin to get stretched ahead of the next trough as upper ridging
amplifies. Thus, the fronts motion will be sluggish and expect most
impacts on Wednesday, but there is some variability in model timing.

The front does have a few things going for it, like good height
falls, decent thermal gradients, and a high shear environment. On
the other hand, CAPE values look to be 250 J/kg or less and low-
level convergence will be lacking without appreciable northwest
winds behind the front due to a secondary system right behind.
Additionally, the North Country will not be located in a favorable
jet placement for upward motion. Overall, anticipate a line of
showers to track eastward throughout the day on Wednesday.

Timing of the front and clouds make the max temperature forecast for
Wednesday a challenge, but eastern VT will be warmest at least. The
front finally clears the area Thursday, but without any transition
to northwesterly flow, temperatures will not be much cooler behind
the front and there is also a piece of vorticity behind it and some
lingering instability, so the shower chances may linger a bit before
the stronger secondary system comes through. Models do not agree
when that takes place, so will keep a blend for now. High
temperatures should be near normal, but low temperatures will likely
be slightly above normal.


Through 00Z Sunday...VFR expected for most of the TAF period.
With most cloud cover finally gone, temperatures could fall
quickly allowing KSLK and KMPV to reach their crossover
temperatures and allow for some patchy dense fog to once again
develop. The best time frame for this will be 06Z-12Z with any
fog quick to lift on Sunday with less sky cover than today.


Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: Mainly VFR, with areas MVFR possible. Chance SHRA.
Wednesday Night: MVFR/IFR conditions possible. Chance SHRA.
Thursday: Mainly VFR, with local IFR possible. Chance SHRA.




NEAR TERM...Clay/Hastings
LONG TERM...Haynes
AVIATION...Clay/Verasamy is the U.S. government's official web portal to all federal, state and local government web resources and services.